Skin cancer is a significant burden in light-skinned populations. Ultraviolet radiation (UV) is the most preventable cause, so effective sun protection is needed. Research on the health benefits of vitamin 0 complicates sun protection advice, for sunlight is an abundant source of vitamin D. Calls for sensible sun exposure may cause people to overexpose their skin to UV. Cell phones with time and location information and data services that can access UV forecasts could help Americans manage sun safety and sensible sun exposure decisions. A multidisciplinary team of behavioral and atmospheric scientists, epidemiologist, dermatologist, and programmers will produce a prototype software, "Solar Cell," for smart phones to support sun protection (time to sun burn and sunscreen use) and exposure (for vitamin D) and demonstrate its feasibility with non-Hispanic Whites and Hi spanic Whites. Advice will be based on personal and behavioral data (e.g., skin type, sunscreen and clothing use) and geo-spatial data (e .g., forecast UV Index). Objectives for this 6-month project are to: develop a fully functional Solar Cell prototype, develop software design specifications, demonstrate online and offline operation and interoperability, convene focus groups with potential end-users, outline operation manual and primer for consumers, and provide reports to NCI.